Algebra Examples

$r^{2} - 81$

Step 1

Rewrite $81$ as $9^{2}$ .

$r^{2} - 9^{2}$

Step 2

Since both terms are perfect squares, factor using the difference of squares formula, $a^{2} - b^{2} = (a + b) (a - b)$ where $a = r$ and $b = 9$ .

$(r + 9) (r - 9)$